Tibullus, born ?, died 19 BC, was a prominent Roman poet during his lifetime, and many today count him among the very finest writers of Latin, although we have only a small amount of his writing: in the Oxford Classical Texts edition of his works by John Percival Postgate, 2nd edition, 1915, in the printing of 1982, the two books of his elegies cover just 46 small pages; then come 29 more pages of poems, referred to as books three and four, some of which probably were written by Tibullus, some probably by Sulpicia, and some probably by someone else.
This collection by Tibullus and pseudo-Tibullus was found in the 14th century, and then lost again, but not before it was copied. The text of Tibullus as the modern reader knows it depends primarily on one such copy made in the 14th century and two in the 15th; the edition which Scaliger made in 1572, which contains material from another lost manuscript; and excerpts of Tibullus' works in various Medieval florilegia. A florilegium is a type of anthology which was very popular during the Middle Ages, compiled from the works of various authors.
After some mentions by his contemporaries Horace and Ovid, and some very high praise from the rhetorician Quintilian (c35--c100 AD), the first trace we have of Tibullus' poems is in an 8th-century list of books at Charlemagne's court at Aachen: "Albi Tibullus lib II." ("Two books by Albus Tibullus.") There are two traces of texts thought to have been copied, directly or indirectly, from this book recorded in the 8th-century: an 11th-century florilegium from Freising containing excerpts of Tibullus; and a 12th-century catalog from Lobbes which mentions "Albini Tibulli lib III."
Around the middle of the 12th century, at Orleans, a florilegium was made which is now called the Florilegium Gallicum, which quotes Tibullus extensively. There are at least six surviving manuscripts of the Florilegium Gallicum. Parts of it, including quotations of Tibullus, were used by Vincent of Beauvais in his early-13th-century encyclopedia Speculum Maius, which was very widely-read in the Middle Ages. There are now hundreds of manuscripts of the Speculum Maius which have survived to our time. In addition to this, several other florilegia copied material by Tibullus directly from the Florilegium Gallicum.
In the middle of the 13th century, a manuscript of Tibullus is mentioned in another library catalog, this time the library belonging to Richard of Fournival, the Chancellor of the Cathedral of Amiens from 1240 to 1260: "Albii Tibulii liber epygrammaton."
Finally, in the 14th century, the oldest copy of Tibullus' works was made which we still have, now owned by the Biblioteca Ambrosiana in Milan: Ambrosianus R sup 26, called A. All the other surviving manuscripts containing the entirety of Tibullus' works come directly or indirectly from A. (That is: they are copies, or copies of copies, or copies of copies of copies, etc, of A.)
But when I say "the entirety of Tibullus' work," I mean the entirety of what we now have which we know or suspect he wrote, plus some other things most likely mistakenly attributed to him: the 46 small pages, plus 29 more, which I mentioned above. If we take just the 46 pages which we're sure he wrote, it's about one tenth as much writing as we have by Lucretius. About one fiftieth as much as what we have from Livy.
How much more did Tibullus write, which didn't survive all the way to the 8th century? Nobody knows. He is said to have written a great many works, but there's little reason to believe all that has been said about him in that regard. Maybe he did write a great deal, and most of what he wrote disappeared some time before Charlemagne. Or maybe he wrote very little. Maybe the poems by him which we have are so very polished and elegant because he wrote very slowly and painstakingly. We don't know. We also don't know how much time he had to write. He was involved in politics and took part in military campaigns. And he may have been born as late as 48 BC, which would mean he was 29 years old when he died. Maybe he was born as early as 55 BC. That would mean that he lived for 36 years.
The small surviving amount of Tibullus' work which we have puts him the middle of, on the one side, the other ancient Latin writers for whom we have a medium-sized volume's worth of work or more each; and on the other side, those of whose work nothing at all survived except a quote or two in the work of other ancient authors, or in a florilegium or a Medieval work of history or philosophy or elsewhere, as well as those who have been mentioned, but not quoted at all.
And, as far as I can tell, we have no way of knowing how many more authors there may have been who were very well thought-of in ancient Rome, well thought-of enough to be mentioned by other writers, but only in some piece of writing which we don't have anymore. Horace mentions Tibullus. The surviving work of Horace fills one volume which might be called either slim or medium-sized. Probably the latter. Some say it's unlikely that Horace published more than what we have from him today. If that's true, it makes Horace quite unusual among ancient Roman writers. We know that many others wrote many times more than what has survived. We have know way of knowing whom may have been mentioned in all of those lost works. Ancient Roman literary life could have been much more crowded with talent than it is sometimes pictured to have been.
Great amounts of ancient Greek literature which was lost has been found again since the 19th century, in papyri preserved by the dry climate in Egypt and other parts of the Middle East. Recoveries of lost ancient Latin texts have been tiny compared to the finds in Greek. Every now and then, something written in Latin will be found among all those Greek papyri. For a while, from the 18th century onward, many lost works of ancient Latin were found in palimpsests. (Not many compared to the Greek papyri, but still.) Nowadays, it seems that the most promising place to look for lost Latin texts is in cartage: in parchment which was made into book covers. I don't know how they take those book covers back apart in order to read what was on those pieces of parchment, but they're doing it.
When I see an 8th-century library catalog, I see a clue toward finding a manuscript which is 8th-century or older. When I see a mention of a missing text in a 6th-century author, I see a clue toward recovering that lost text. I don't know enough about such things to know whether that makes me refreshingly optimistic, or just foolish. It does seem to make me unusual, and the great sharpness of mind of the many specialists in Classical Studies makes me think that it's realistic to consider such hopes as simply foolish. Still. I see clues.